Automatic telephone system



Feb. 19, 1929.

R. G. RICHARDSON ET AL AUTOMATIC TELEPHONE SYSTEM Imran nrs Emi-Lag ?.Bwhars Url-Har m L- Nesgn Feb. 19, 1929.

R. G. RICHARDSON El' AL AUTOMATIC TELEPHONE SYSTEM m W t .ls E. E w M .S m ...nl a im s n r E E .U 2 ml n l l .QW www MAM m HBH. mwk r. m .m d .L .m E. F E a ...y fm D E Feb. 19, 1929. 1,702,392

R. G. RICHARDSON ETAL AUTOMATIC TELEPHONE SYSTEM Original Filed March 29. 1922 9 Sheets-Sheet 5 Feb. 19, 1929.

R. G. RICHARDSON ETAL.

AUTOMATIC TELEPHONE SYSTEM Original Filed March 29. 9 Sheets-Sheet 4 JAN.

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Feb. 19, 1929. 1,702,392

R. G. RICHARDSON ET AL f AUTOMATIC TELEPHONE SYSTEM Original Filed March 29. 1922 9 Sheets-Sheet 5 Rodney EHI/:hard'smn-Haf LNEsm-L Feb. 19, 1 929. 1,702,392

R. G. RICHARDSON ET Al.

AUTOMATIC TELEPHONE l51151211111 original Filed March 29. 1922y 9 sheets-sheet e EIT-5 Feb. 19, 1929.

R. G. RICHARDSON ET AL AUTOMATIC TELEPHONE SYSTEM Original Filed March 29. 1922 9 sheets- Sheet 7 "FILL BUCfnEi/r E Emhard'sun-#Hell L Nelsnn Z. En-ZL- Feb. 19, 1929.

R. G. RICHARDSON ET Al.

AUTOMATIC TELEPHONE SYSTEM Sjlt 8 I I I I I 'Ill'.

E Lf E Bwharnrsn-Har m LNEZEUU.

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R. G. RICHARDSON El' AL AUTOMATIC TELEPHONE SYSTEM Original Filed March 29 1922 9 Sheets-Sheet 9 gli 1:29:13

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Patented Feb. 19, 1929.

UNITED/STATES .PATENT OFFICE.

RODNEY G. RICHARDSON, or CHICAGO, Ann MARTIN i.. NELSON, or'rARK lunedi,`

ILLINOIS, ASSIGNORS, :BY MESNE ASSIGNMENTS, T0 AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION 0F DELAWARE. Y

AUTOMATIC TELEPHONE SYSTEM.

Application led March 29, 1922, Serial No. 547,866.V Renewed. December 24, 1928.

The present invention relates in general to automatic telephone systems, but` more especially to multi-ottico automatic telephone systems; and the objectofthe invention is to produce a new and improved cfdirector, or registering, translating, ratus, for controlling the automatic switches,

and new and improved grouping or trunlring arrangements for such directors.

In our prior application Serial blo-538,551, iilcd February Q3, 1922, anapparatus of the above character is illustrated and described. The director shown in that application is f in Amotion' and transmits series oi impulsesin CII vaccordance* with` a code .derived by a trans,- lation from these letters. v ,The codeimpulses operate a series or selector switches to trunk the call to the desired ofce, and the sending deviceY then transmits the registered digits in the called telephone number to the selected i yottico without ytranslation toV operateother selectorsand a connector to complete tliecon nection to-,the called line.` Means y is provided whereby the'transmission of any series of impulses except the first is made contingent upon the completion of the trunk hunting movement in the selector which responds to thepreceding series of impulses.

The director forming the subject-matter of the present invention resembles the one above referred to, and operates according to thesame general-principles, butv is simpler and is less expensive to manufacture. .There are ay number, of new features among which may be pointed out the following: y j

According to the principal feature of improvement, the directors are divided into groups. and director selectors arel inserted between the first selector trunksY and the die rector-s. This arrangement reduces the number of different calls'handled by each direc tor to approximately one-tenth'ot the total number, whereas in the former system each d'lrectorhad to be capable ofhandlmgall and sending appal saving in particular which may be mentionedv 1s brought'about by the use of only one two# motion Strowgerswitch per director, instead or the nine which were formerly required. Y Various modiiications of the general grouping plan arepossible, as will be'pointed out.

A second feature is the elimination ofthe revertivecontrol of the sending switch by means of which the starting of the sending switch to operate any selector was made contingent on the completion of Vthe trunk hunting movement or the preceding selector. Instead of thc revertive control, a standard time interval of approximately one-third of a second is inserted between successive ,series of impulses, thistime interval being'slightly longer than the maximum hunting ktime of a Strowger selector switch. Y

A third feature is a simple and inexpensive directorl for calling long distance. A group of these directors is accessible from the 0 level oit the director selectors.

,Other features relate mainly to ycircuit im'- provements and will bepointed out in detail hereinafter. 1 l l Referring to the drawings, Figures 1 to 6, inclusive, are circuit diagrams of suiiicientof the apparatus used in a complete director system to-illustrate the preferred =form of the Y invention,Fig.` 1 being a circuit diagram of a iirst selector trunk and a director selector;

Figs. to 5, inclusive, being circuit diagrams of,v a complete directorior use in handlmg regular traffic, while Fig. 6 isa circuitfdia# gram oi a long distance director.

Figure 7 is a circuit diagramof a modi-- fied form, of first selector trunk equipment which may be substituted for Fig. l.

Figure 8 is a trunlring diagram of the sys` tem ,which is shown in detail in Figs. l to 6, inclusive. v

Figures 9,10, and 1 are diagrams of modified trunlring lor grouping arrangements which are desirable 'in some cases. Y

. Figure 12 is a tront view of the subscriber s calling device showing the numbering of the dial.

1 to t5, inclusive, shouldV be oined together.

Figure 13 is a layout showing'how sheetsv It will .beV advisable `first to consider the grouping andtrunlring layout, Fig. 8,'as an understanding of this will assist in the explanation of the rest of the drawings. The trunklng diagram, Fig. 8, is intended principally to show the grouping of the directors,`

although a number of switch trains are illus-` trated also which will be of assistance .in explaining the operation of the directors. It may be stated at the outset thatithe illustration of the trunking is only fragmentary. Each office in the system is provided with first, second, and third selectors for handling the interoiiice trunking, and in any given office the trunk lines extending to the other offices are in general taken from the banks of the third selectors, although a certain number of offices may be reached directly from the second selector banks. Assuming. that in a particular case a group of interoiiice trunk lines is taken from a third selector level, these trunk lines would extend by way of repeaters to incoming fourth selectors at the terminating oflice, and connections would be completed at that office by means of the incoming fourth selectors, fifth selectors and connectors. An arrangement similar to this is shown diagrammatically in Fig. 8. The subscriber at substation A in t-he West office may set up a connection with the subscriber at substation A1 in the Torrington office by means of the primary and secondary line switches C1 and C, and a director in group No. 4, which director is adapted to register the called number TORl-ington 2845 and operate the first, second, and third selectors E1, E2, and E3 in the originating office, and the fourth selector E4, the fifth selector E5, and the connector H in the terminating office to complete the connection.

A connection from the subscriber at station A to the subscriber at station A2 in the Lothair oihce may be established in the same manner with the exception that 'since the Lothair oiiice is a tandem office, an additional selector will be employed. A director in the fourth group is used, and the connection is established by means of selectors El, E2, and E3 in the `originating ofiice, and 'selectors E, E55, and E6, and connector H1 in the terminating office. It may be stated that'the incoming fourth selector E44 has access to a group of trunks extending to loca-l fifth selectors on one level and on the other nine levels has access to groups of trunks extending to other oflices. For instance, the fourth level may contain terminals of trunks which extend by way of repeaters such as repeater R3 to another ofiice.

The trunking of calls to the various special operators indicated will be suiiciently obvious from the foregoing, and at any rate will be described fully in the course of the detailed explanation of the system.

An explanation of the grouping of the directors necessarily entails a brief discussion of the directory numbering system. The exchange names are retained, as in manual systems, and each subscribers telephone number, that is, the number which has to be dialled, consists of the first three letters ofV his exchange name and four digits. Inuthe directory the first three letters of the exchange names are printed in capitals and preferably also in heavy type in order toV distinguish these three letters from the others and thus avoid confusion on the part of the subscribers. The calling device dia-ls are, of course, marked with letters in addition to the usual digits, as indicated in Fig. l2.

`It may be perceived now from an inspection of Fig. 12, that all the offices or exchanges of the system fall into nine natural groups in accordance with the finger holes in which the initial letters of the exchange names appear. There would, of course, be ten groups, butfor the fact that the digit 0 is used for long distance, which makes it impossible to have any exchangenames beginning with the 'letter O. To explain the grouping of exchanges a little more in detail, all the exchanges the names of which begin with letters I or P constitute the first group, while all those exchanges the names of which begin with A, J, or R constitute a second group; Similarly, the other seven groups are composed of those exchanges whose initial letters occur in finger holes 3 to 9, inclusive. `When the initial letter of any exchange name in the first group is dialled one impulse will be transmitted, when the initial letter of any exchange name in the second group is dialled two impulses will be transmitted, and so on.

From the above facts it will be obvious that the dialling of the first digit might conceivably be utilized to select the group of exchanges which includes the exchange in which the desired subscriber is located, but it cannot do this directly in the sense of actually trunking thecall to a switching point for the group, because the trunking is all done 1n accordance with a code which is not'definitely determi ned on until the third letter is dialled. The same result may be accomplished indirectly however by providing as many groups of directors as there are group of oiiices and by using the first digit to select a group of direcis normally open at this point. From ,the re-V lay equipment D the incomingand outgoing sections of the trunk extend tothe director selector F. When a calling subscriber who has seized the trunk line dials the first letter of the called number, the selector F is oper-v Cil ated over theincoining section ot' the trunk` Theoretically, there should beten groups of directors, nine groups for handling the regular traflic, and one group for handl long distance calls; but inV piacticeit Will often'be foundv that the'tull nuniberof groups is not necessary. i There are tivo cases in which the number otV groups can be reduced, both of Which are illustrated in Fig. 8. The first case is Where there is no conflict between the exchange names intwo different groups of exchanges, which makes it'possible to use one group of directors tor 'handling trailic to both groups of exchanges. Forv instance, it may happen that in a certain system the second and third'letters in the naines ot all theexchanges in the iirst group, t'orin .difterent tivo-letter combinations than do the second and third letters the exchange naine of any exchange in the fourth group. lllhen this is true, the irst letters in the exchange naines are not needed to distinguishthe e2:- changes from each other, and vall the ef;- changes of the first and fourth groups maybe combined into onegroup served by a single group of directors. This arrangement is illustrated in Fig. 8, in Which the lirst group of directors is omitted, the first level ci' the director selector F being multipled vvith'the fourth level.' The No. 4f group ot directors handles the traffic tothe exchanges-in the tlrst group yas Well as thetraiiic to the exchanges in the fourth group. l l

The second case is where certain groups are entirely missing, that is, when there are certain groups of letters which do not occur as the initial letters in any exchange names. In the present :case it Will be assumed that there are no exchanges the names ot which begin with letters G, X, H, or Y. vLetters Gr and X correspond to the eighth level, While letters H and Y correspond to the ninth level, and accordingly these tivo levels are multipledtogether and give access to a'sinall group or" special directors, similar to the longl distance directors, which trunk calls accidentally arriving at the eighth and ninth levels to an operator. f v

The grouping illustrated will now be readily understood. Therefare six ygroups ot reejular directors, numbered from 2 to 17in the drawing, and accessibleroni levels l to 7, inclusive, `which are provided for handling tra-flic to exchanges in groups l to 7, inclusive 'and two groups ot special directors, one of which is accessible troni the tenth level and is used for handling long distance calls, While the other group is accessible ironitlie eighth and ninth levels and is used tor handling calls Vaccidently arriving at the dead levels of the director selectors.

The number ot directors in each group will, orP course, vary in accordance With'the trai"- tic which the directors are required to handle, which in turn depends on thenumber and size of the oiices in the groups. In some cases it may be that not more than .ten directors are required in a group. In a case ot this hind the trunliiig trom the director selectors to the directors is exceedingly simple, tor asis Well lrnoivn a selector switch ot th Stroivger type has access to ten trunk lines on each level and each director Vselector may have direct access to all oic the directors. .F or instance, it the tratiic to the offices in group No. 3 is such as to require only ten directorsto handle it, thcrewould be only ten directors in the No. 3 group and the trunk lines e1-tending to these `lircctors` would be multipled in the' third level ot all the director selectors such as the director selector F. Another. group of eX changes may include so many exchanges that the tratlic requires tteen directors to handleVV it. Assuming thattlie No. 2j group of eX- changes is ot thissize, there y.vould be fifteen directors inthe No. 2 group, Which would require al slightly different t'runlting arrangement. A, convenient method .of procedure would lbe to divide the director selectors such as tlieselector F into two groups, sotar as the second` levels thereotis concerned, and terminate the tru'nlr lines from directors l to l0 inthe second level oit the tirstV group. While directors 6 to l5 would be terminate'c inthe second level L *l would make tivedirect'orsot the second group individual to each group ot' director selectors, and ve common to both groups. An elaboration of this idea VrWill serve in the case of still larger groups oi directors. For instance, it may be thatY there are titty ldirectors in the fourth group. vThe director selectors Would then be divided into nine groups vvith respect to their fourth levels, and the iirst 'group may be given access to directors l to lO,'t-he second group to directors .6 to l5, the third group to directors 1l to 20, etc. TWhere such large groups are involvedit may be desirable, invorder to increase the etliciency,to combine them all into one group by means or secondary ,line switches in accordance with the Well` oi tnesecond group. vThis iio iff() Jill lli

. switch requires no relays.

until after the system embodying the preferred arrangement has been fully described.

The apparatus inFigs. 1 to 6, inclusive, may now be explained more in detail. Fig. l shows the detailed circuit arrangements oi the first selector trunk which is depicted in Fie'. 8 together with the associated director sc lector. The trunk conductors l0, 1l, and 12 extend from multiple sets of contacts in the banks of secondary rotary line switches such as the line switch C2, one oi' which sets of contacts is indicated by reference characters 22, 223, and 24, by way ot the relay equipment D to the iirst selector E1. The relay equipment D comprises a single relay, and the line conductors of the trunk are normally open at contacts ot this relay, both the incoming and outgoing sections or" the trunk being extended to the director selector F which is located directly below the trunk relay equipment D. The first selector El and the director selector F are vertical and rotary switches of the Strowger type, and each has access to sets of contacts arranged in ten horizontal rows or levels. The circuit oft the iirst selector El is a standard two-wire circuit such as is in common use, and the circuit of the director selector Fis very much the same, although it has been modified somewhat in order to take care oi the somewhat dilierent functions which the director selector has to perform.

One of the directors for handling regular traiiic is shown complete in Figs. 2 to 5, inclusive, and comprises the master digit controller M, Fig. 2; the B and C impulse register J, Fig. 4; a thousands register M1, a hundreds register M2, a tens register M3, and a units register M4, all of which are shown in Fig. 2; an impulse sending switch S, Fig. 3; a sequence switch S1, Fig. 5; and an intermediate distributing frame I. D. F., Fig. 4.

The master digit controller M and the four digit registers M1 to M4, inclusive, are simple ten-point step by step switches, each of which is provided with an operating magnet and a release magnet, and a set of oli normal springs which are operated when the switch lwipers are advanced out of their normal position.

The B and C impulse register J is a Strowger switch of the vertical and rotary type having 100 sets of contacts arranged in ten horizontal rows or levels. The operating and release magnets of the switch J are controlled over conductors coming Jfrom the master digit controller M, Fig. 2, and consequently, the Four wipers are provided, indicated by reference characters 306 to 309, inclusive, and shown to the right ofthe operating magnets in Fig. 4, which also shows thc first five sets of contacts in the tenth level of the bank to which these wipers have access. All of thecontact sets in the bank which correspond to vvorking` exchanges, orwhich correspond to exchanges which it is anticipated will be installed, are wired `to terminal sets on the lett-handside oi the I. D. F., as isshown in the case of the second, fourth, and fifth contact sets; while all those contact sets which do not correspond to working exchanges, are multipled to.n gether and are connected to a single set of terminals on the lett-hand side of the I. D. F., as is shown in the case of the rst and third Contact sets. Ot course, it desired, all of the contact sets could be connected to the letthand side oi the l. D. F. in regular rotation without regard to whether they are actually in use or not, but the strapping of the dead contact sets mentioned above is recommended as a method oi decreasing the size of the intermediate distributing frame.

The right-hand side of the'intermediate distributing `trame consists of iitteen or more bus-bars, each having a plurality of terminals in order to provide facilities for cross-connecting any terminal on the left-hand side of the I. D. F. with any busbar. The tirst nine bus-bars correspond to the nine digits, 1 to 9, inclusive, and. are so marked in the drawing. These bus-bars are connected in multiple with the banks of the register switches M1 to M4, inclusive, and with the bank of the sending switch S, as is shown in Figs. 2 and 3. Busbars X., Y, and Z provide for automatically advancing the sequence switch S1 on oiiice codes which have less than the maximum number of series of impulses; busbars S101 and Sie2 are special switching bus-bars which are used to control the switching through at the trunk equipment D when calling the operators or similar numbers; while the busbar RL is associated with a special relay which is used to trunl: calls to an operator over a route which requires a greater number of series ofcode impulses than is provided orin ordinary cases. y

The intermediate distributing i'rame represented diagrammatically in Fig. 4 is assumed to be of a standard type, with standard terminal arrangements on one side and a series ot' bus-bars on the other side, and having permanent cable connections between the lett-hand side and the bank of the B and C impulse register J, and permanent cable connections from the bus-bars on the right-hand side to the banks oi the register and sending switches. It desired, however, this standard type of construction can be deviated :from to a considerable advantage, at least so iar as the initial cost is concerned. @ne method. oi' procedure which has been favorably considered, is to mount the busbars as a unit directly in the rear of the bank of the B and C register switch, which will permit jumpers to be run directly from the bank of the switch to the bus-bars. This arrangement permits the terminals on the left-hand sidefof the' frame to 'entirely omittedv and will eliecta considerable saving. The sending switch S, Fig. 3, and thesequence switch S1, Fig.l 5, are step bystep rotary switches of the type in-Which the Wipers move yin a forward direction only. In further explanation orl these switches it shouldbe stated that they are. oit the type in `Which the Wipers are advanced When the.

stepping magnet retracts its armature rather' than When the stepping magnet is energized.V The general object and scope of the 1nvention having been pointed out, the operation of the apparatus. involved Will now be described more in detail, and for this purpose it Will be assumed first that the subscriber at 'station' A, Fig.,8, desires to establish` a connection with-the subscriber. at station A1,

Whose telephone number is TORrington 2345.

Then the receiver is removed at station A,A

land 1Q, and la circuitvivill be completed over the said trunk conduct-ors and conductors' 60 and 6l for the double Wound line relay 64190;F the director selector F. vRelay 64 is J accordingly energizedv at armature 72and closes a circuit for the slow-acting release relay65. On energizing, the latterrelay connects ground to conductor 76 at armature 74, andv at armature connects ground to the release trunk conductor 11. The latter l operation completes a holding circuit for the operated line switches in the usual and Well understood manner. y

The calling subscriber Willnovv operate his calling device dial in accordance `With the` first letter :T of the calledfnumber, as a result of which four'interruptions Will be -produced vin the circuitof his line, andthe line relay 64 of the director selector F Will be deenerf gised iour times. Ateach deenergizationthe line relay 64 transmits'an impulse of current to the vertical magnet 69k over a path which extends Jfrom vthe grounded conductor 76' by Way of the resting contact of armature 73 and thesaidarmature, armature-88 andits resting contact, Winding of the' slow-acting.v

series relay 66, and thewinding ofthe vertical magnet 69 to battery. B'y-theop'eration of the vertical magnet responsive to these impulses, the Wipers to v88, inclusive, are raised step bystep and are'brought'to rest:

opposite thel fourth level of bankcontacts. Relay 66 is energlzedln series VWith the vertical magnet 69k 'and sincelt,isslow-acting, it

holds its rarmature attracted-during' the vertical movementof the switch. ,y On the first vertical step the'o normal springs are shifted and a circuitiscompleted from the grounded V,conductor 63 by Way of the Work-A ing contact ofv armature 77, ofi normal springs 78, and the Winding of the stepping relay to battery. Upon energizing, relay 67 establishes a locking circuit for itself at. armature y7 9 and at armature-80 preparesa circuit for the rotary magnet 70. An instant after the vvertical movement of the switch is completed, the slow-actingl relay 66 falls back and completes the circuit 'of the rotary magnet .70, Which energizes and ad varices the Wipers 85 to 88, incluslve, into engagement Withthe first set of contacts in the level opposite which they'vvere raised. Near the end of its strokethe arrnaturekoil the r0-`V tary magnet 70 opens its interrupterJ contactand breaks the locking circuit ofthe stepping relay 67, andthe stepping relay thenv falls back and breaks Vthe circuit of the ro tary magnet, which accordingly falls back asv also andagain closes its interrupter contact.l l

If the irstset of contacts isybusy, there will be a ground potential on the test Contact engaged by the. test Wiper 87 ,y Vswitching relay 68 Will remain short circuited, andthe stepping relay .67 will'be reenergized to 'again' close they circuit of the rotary magnet 70.l The rotary magnet will thus-be operated a second time and theswitchwipers Will be advanced into engagement kWith the second set.v of contacts; in the fonrthlevel. `This oper-V ation, it may be statedv isrepeated as1long as thev test Wiper 87 continuesgtok encounter ygrounded testcontacts. When an idle testv contact is reached, Which We Will assume to be the test contact 91 ofthe trunkline ex;- tending to the director equipmentshown in Figs. 2 to 5',.inslusive, the test wiper v87 Willl `find no ground potential, themsteppingjrelay 67 Will not beenergized' again, and the rota-4 tion o' the switch will cease.' Thesvvitching' relayv 68, beingnonr no longer short'circuited, lsvene'rglzed over a clrcult extendlng from the grounded `conductor- 76 by Way .of the' Winding of the said relay 68, the-interrupter` Contact of the rotaryi magnet, V the ofi? `normal springs 78, and the Winding of the lstepping relay 67. The latter relay, it may be meny .tioned, is not operated at this timey because of the relatively high'resistance of the switch` ing relay 68. l ,v Y.

When the switching relay 68l pulls up' at the end of the selecting movement of the di-` rector selector F ,fa considerable number yot circuit changes are brought about. At arma-vr ture 84, of relay 68 `the groundedconductorlV 76 is connected :direct to the testV Wiper 87, and a ground potential is thusplaced upon the test contact 91 and its multiples in the f banks kof other director selectors inv'order toi make-.the :selected director busy; v A ground potentialis Yalso placed on, .the holding con- .tors 100 and 101.

ductor 102, and since this conductor is con-y controller M, on attracting its armature 209,

connects the common conductor 299 coming from the timer T tothe ivindingot relay 205, and at armature 217 prepares a circuit for relay 206. i

Another result of the energization oit switching relay 68 in the director selector F, is` the shifting of the local operating circuit from the vertical magnet to Wiper S6 at armature 83, which results in the preparationA of an impulsing or control circuit for the vertical magnet 303 of the B and C impulse register J, Fig. f1, which may be traced asifolloivs: from the grounded vconductor i'l by Way of `the resting contact ot armature 73 and said armaturetsince theline relay 64 is nov/.energized the circuit is noiv open atthis point),'armature 83 and its Werking contact, WiperBS, bank contact 92, conductor 1053,` armature land its resting contact, conductor 202, the Winding of the low re sistance sloW-actingseries relay 207, Wiper 218 of the master digit controller M in first position, conductor 801, and the Winding of the vertical magnet303 to battery. lThe preparation ot this circuit places the B and C impulse register J in condition to receive the next two series of impulses from the callingline.` 1

a further result et the energization et the switching relay 68, theconductors 25 and 26 `which are normally connected Withthe trunk conductors `20 and 22, extended at armatures 81 and82 to thewipers 85 and 86, respectively, and are tluis connected by Way of bank contacts `89 and 90 with conduc- This operation completes a bridge across the trunk conductors 20 and 22Which may be traced from the trunk conductor 20 by Way ot normally closed contacts controlled `,by armature 111, conductor 25, working contact of armature Sland said ar mature, Wiper 85, banlrcontact 89, conductor 100, resting contact ot armature 123 and 'the said armature, armature 137 and its resting contact, conductor 101, banlr contact 90, Wiper 86, armature 82 and its Working contact, and

normally closed Contact springs `controlled by armature `18 to the trunk conductor22.` Upon the closure oit the circuit above traced, the line relay30 ot the selector Elvis' energized disconnects relay and establishes a circuit for thesloW-acting release relay 31. On energizing, the latter relay grounds the release trunk conductor 11 at the upper armature, and at its lower armature prepares a circuit for the vertical magnet 35.

When the calling subscriber operates his calling device for the next letter in the called number, or the letter O, ten interruptions will be produced in his line circuit and the line relay 611 in the director selector F Will be deenergized ten times. Accordingly, the line relay 6i will transmit a series of ten impulses over tliepreviously traced operating circuit to the vertical magnet 303 of the B and C imulse register J. In res )onse to these im`V pulses the magnet 803 operates to raise the Wipers 306 to 309, inclusive, step by step until they stand opposite the tenth level ol' bank contacts. v

The slow-acting relay 207v in the maste digit controller M is energized in series with the vertical magnet 303 of switch J and retains its armature 215 in operated position throughout the series of impulses. At the working contact ot armature 215 a circuit is completed for relay 208 which is thus maintained energized also. series oit impulses relay 207 falls back' and breaks the circuit of relay 208, whereupon the latter relay deenergizes also.` Since relay 208 is sloiv acting, however, it Will not de-v energize until an instant after relay 207 has retracted its armature and a momentary impulse et current will be transmitted to the stepping magnet 212 oi" the master digit controller M from ground 'by Way of armature 215 and its resting contact, armature 216 and its Working contact, and the Winding oithe stepping magnet 212 battery. By the operation ot the stepping magnet 212, wipers 21Sand 219 are advanced into second posi tion. It will be noticed that Whenrela-y 207 energizes, it disconnects ground lfrom the lower terminal of relay 206 and causes relay" At the end ot the 206 to 'tall back in case it has been previously energized by timer'l, and relay 205. Relays 205 and 206 are provided in order to switch the call and free the director in case the callino' subscriber should tail 'tocomplete his number, und in the ordinary operation of the system these relays liaveno function.

llfhen the calling subscriber dials the next letter in the called number, or `the letter R, tvvo interruptions will be produced in hisline circuit and the linerelay 64 oli' the director selector `will be deenergized twice. This relay'accordingly transmits two impulses of current over the previously traced operating circuit, and new since the Wiper 218 of theV master digit controller M is standing in sec ond position, these current `impulses will pass over conductor `302 and through the rotary magnet' 304. By the resulting operationef the rotary magnet wipers 306 to 309, inclusive,

v yregisterJ to the stepping vmagnet 227 of the the slow-actingv relay y208.

rotary movement these two relays deenergize C impulse register lJ, thel slow-actingV series relay 207 of thefmaster digit controllerl isv `energized the same as it was during the vertical movement, and completes a circuit. for At the end of the aninstantapart and thus cooperate in transmitting an impulse of current to the stepping magnet 212 of the master digit controller M, the `wipers of which accordingly advance to third position. A At wiper 218 the operating or control circuit coming from the director select orrFover conductor 202 is shifted from the rotary inagnetof the B and C impulse thousands register M1, while at wiper 219 i a ground is placed on starting conductor 400.

'Responsive to the grounding 'of thev start wire400, the sending switch S begins to transfv mit impulses in accordance withl the ofiice code which has been determined. on by the dialling. of t-he first three letters of the called number, but it is thought best 'to defer therefrplanation of thesev operations inorder to .permitV an explanation of the operation of the register' switches M1 to .M25 inclusive, in registering the fourl digitsof the called number. When the calling subscriber operates his calling device'in accordance with the digit 2 of the called number, lthe linerelay 64ofthe director selector F responds in the usual manner and ytransmits two impulsesv to the stepping magnet227 of, thetliousands register ylv, 1. By the operation of the stepping; magnet 22'.7 wiper 244 is advancedtwo'stepsV into engagementwith the secondv contact in its associated bank. 'Wli'en thev switch leaves its normal position the oiinorinaljsprings vare shifted and spring 236y by engaging its working contact kprepares a ycircuit for grounding conductor42l which iscempleted when thek slowactings'eries relay 231 deenergizes at the end i of-,theseries of impulses. Relay ,231, it may bestated, is energized in series with thestepping magnet 22T and holds itsarmature 235 attracted during thev stepping 4movrnnent Aof Athe register .switch in order to prevent the conductor42l fromA being grounded until the i, registration of the digit is completed.

The'slow-:acting series relay 207 is also en ergized in fseries with the stepping VmagnetY 227 and inr conjunction with relayv208operates to transmit another impulse of current to the stepping magnct2l2'ot the master digit y'controller lato-the proper time, whereby wipers i 2l8vand 219 are advanced to the fourtli'position. `Wiper 2l8 in shifting from third Vto Vfrom the istepping.magnet 227 of register switch Mt. tothe stepping magnet 225 of f, hundred@ register] switch YM. ,N0 circuit changes are broughta'bout by the further movement of wiper 219, since contacts 3 to '10, inclusive, in the bank associated with this wiper are multipled together. It may be stated that wiper 219 should preferably beso constructed that when advanced from contact to contact it will engage a new contact each time before it disengages thepreceding one.

lt will be unnecessary to describe in minute detail how the other three register switches M2, M3, and M4 are operated responsive toV Vthe dialling of the remaining three digits of the number. lt will be sudicient topoint out briefly that when the hundreds digit A3 is dialied, the line rela-y 64 will transmit three impulses of current through relays 2,07 and 230 and through the stepping magnet 226 in l serieswhereby the said stepping magnet is operated to advance wiper 245 into'engagement with the third contact in its bank. At the end of the stepping movement relayl 230 which holds up its armature 234 during the operation of the register switch,` deenergizes and connects ground to conductorf422. -At the saine time the sicwfacting relays 2.07 and 208 transmitan impulse to the stepping mage net 22 of the master digit controller in order to advancethe wipers 2`l8and 219 to fifth posi tion. the calling vsubscriber dials the tens digit 4 and the unit-s digit 5, a series of four impulses is iirst transmittedtothe steppinginagnet Y22H5 of the tens register Mrand a series of In a mann er similar to the ahove,wheii five impulses is then transmitted to the step- 'i inUr magnet 224l of the 'uiiits register M4 Yit e n a a being understood, or course, thatv the i control circuit is shirted'from magnet 225 to. magnet 224 at the proper time by wiper 218 of the master digit 'controller iM. Viper 246:01@

register switch M3 is accordingly advanced icc into engagement with the fourth contact in its bank, while wiper 2417' of the register switch M4 is advanced into engagement with the iifth contact in its bank.. Conductors 423 `and 424 aie'grounded v.vhen the slow-acting liu rclays'229nnd 228 fall' back after the coinpletion of the oper-ation V,of theirrespective associated register,switches; f f

lThe oaera ion of the sending switch'S i b A 7 yFig. limay now be taken up. As stated be fore, this switch y'begins operating to .traiis'mit impulses in accordance with the required -ofiice code as soon asthe last of thethree letters. of the nuinber'have beenfdialled, the actual starting of the sending switch being ac'- coinplished-by the grounding of the lstarting wire 400`when the wiper 219 of the master.-v

digit controller M arrives in third'. position'.

lie'codeY in accordance with which the Vcallfis tiunked to the Torrington oiiice .is 554, as may be perc 1ved fromnn inspection of thetrunk- Ving diagram, Fig. 8, and .accordingly,fthe

second'set` ef contacts in the tenth level .this so oros i' battery.

`connected to bus-bar X.

connected at the intermediate distributing frame as to cause the transmission or' three series of impulses, the first series comprising six interruptions, the second series'co1npris- `ing five interruptions, and the third series comprising tour interruptions. More in de tail, terminal 341 is cross-connected to busbar No. 6, terminal 340 is cross-connected to bus-bar No. 5, terminal 339 is cross-connected to busbar ilo. 4, and terminal 338 is cross- These cross-connections will cause the required series of impulses to be transmitted by the send ing switch S, as will be understood shortly.

Conductor 400 extends to thc sequence switch S1, Fig. 5, Where it connected to Wiper 404 and lto the first i`our contacts in the bank ot Wiper 405. Accordingly, when this conductor is grounded, a ground is placed on the No. 0 contact in the bank ot the stop Wiper 114 oit the sending,r switch S, the circuit being traceable from the grounded conductor 400 by Way of sequence switch Wiper 404 in lirst or normal position, conductor 411, Wiper 306 ot register switch .l and the contact now engaged thereby, terminal 341 on the left-hand side of the I. D. F., a jumper connecting this terminal with bus-bar No. 6, and thence by Way of conductor 366 to the No. 6 contact in the bank olf stop Wiper 114 ot the sending switch. At the saine time that the above circuit is completed, a circuit is completed for the impulsing relay 107 oit the sending switch over the following` path from the `grounded conductor 400 by Way ot Wiper 405 in first position, conductor 425. resting contact otarmature 119 and the said armature, resting contact of armature 140 and the said armature, Winding of the impulsing relay 107, and through the interruptor I to The interruptor I is continuously driven, and consists oit' any suitable cam arrangement for intermittently connecting battery tothe relays such Vas relay 107 at the rate oi about ten times per second. When this circuit is closed, therefore, or shortly after wards, depending on the position ot the interrupter I, relay 107 is energized and opens the impulsing contact at armature 123, this operation being of no eii'ect, however, duc to the fact that the Contact at armature 123 is short circuited at armature 120 0i relay 100. Relay 107 'also closes the` circuit oi stepping magnet llatarmature 124, andthe said magnet is energized. `When the circuit of relay 107 is broken by the interrupter l an instant later, the relay falls back, again. closes its interruptor contact, and breaks the circuit of the stepping n'iagnet 115, Which there- A uponV retracts its armature and advances the wipers `113 and 114 one step. A circuit s now completed lfor relay 10G by Wiper 113,

and this rel ay, `upon energizing, removes the short circuit from the impulsing contact 123l at` armature 120,V prepares a lockingcircuit for stop relay 105 at amature 121, and at armature 122 connects ground to conductor 426, this completing a circuit for the stepping` magnet 402 oi' the sequence switch S1; Magnet 402 is accordingly energized, but without affecting the position oit .its Wipers, which like the Wipers of the sending switch are advanced When the magnet retracts its armature. rEhe second time that the circuit of relay` 107 is closed by interruptor I, the said relay closes the circuit of the stepping magnet 115 before and also, since relay 106 nonv energized, it opens the circuit of the line relay 30 ot the selector El at impulsing coi act 123. `When the circuit .ot relay 107 is broken by the interrupter, vit deenergizes and breaks the circuit of the stepping magnet 115, which retracts its armature and advances Wipers 113 and 114 one more step, thus bringing the stop Wiper 114 into engagement with the No. 1 contact in its bank. It Will be seen that the sending switch S is caused to make an initial or false step before control of the interruptor l. After the second Y dcencrgization, which terminates the first impulse or interruption ot' the control circuit, the stop Wiper 114 is advanced into engagement with its No. 1 contact, as stated, after the third dcenergization Wiper `114 is advanced: into engagement With its No. 2contact. and so on, until finally, after the seventh deenergization, and aliterthe sixth interruption has been produced in thecontrol cir-4 cuit, thestop Wiper is advanced into engagement with the No. 0 contact. Siiice the first digit in the interoilice code is 6, the required numbcrot impulses have new been transmitted to the selector El.V As previously explained, the No. 6 Contact the lower bank of the sending,n switch is groun ded at this time, and Whcnithe stop Wiper 114 comes intoen gagement with this contact, a circuit is com# l Jleted for the sto') relav 105. U on' eneriz1n T the sto i rela 7closesa lockinff circuit r3) i to for itself at armature 117, at ari'nature 119 opens the circuit ot the impulsing relayV 107 in order to prevent the transmission of `any more impulses, and at armature 116 complctes an automatic rotary circuit for the steppino; magnet by connecting' Wiper 113 with the said magnet through its 'interruptor position, conductor 412, wiper 307 of register switch J Vand the contact engaged by said wiper, terminal 340, a jumper connecting this terminal with bus-bar No. 5.r and conductor 365 Vto the No. Contactin the bank of the 'stop wiper. The movement of the'ot-her sequence switch wipers is without particular eiect at this time. v

The operation of the yfirst selector E1, Fig.

1, in response to the first series'ot code impulses may now be brie'liy explained. As'described in the'foregoing, the circuit of thellne relay of selector El is interrupted sin times at the impulsing contact 123 in the sending switch S and thesaid line relay is accordingly deenergized siX times. Six impulses are thus transmitted to the vertical magnet which operates to raise the wipers 50,51, and 52'step bystepuntil they arrive at the rsixth level of `bank contacts. 'The slow-acting series relay 32 is energized in series with the vertical niagnet 35 and at the'iirst'upper movement 'of the switch shaft completes a circuit for the stepping relay 33, which latter vrelay establishes a locking circuit for itseltand also'prepares a circuit for the rotary magnet 37 lllt the end of the vertical movement of the switch, relay 32 falls backand closes the rotary magnet .circuit toinitiate the automatic trunk hunting operation. The wipers of the-switch are now advanced step by step by rotary magnet 37 under control of the test wiper 51 and the stepping relay 33. Then an idle trunk is reached,whicli we will assume is the one indicated in thefdrawing,the test wiper 51l fails to find aground ou the test contact 54, and the rotary movement oli the switch is arrested.

Switching relay 34 is now energized in theV usual manner, places a ground on the test wiper 51 in order to makethe selected trunk busy, and vextends the trunk conductors 20 and 22 by way of armatures 40 and 43, wipers 50 and 52, and bankcontactsl 53 and 55 to thel 'switch'is preparedffor its vertical operation, and a ground 1s placed upon the release trunk conductor 57 r Returning Vnow to the sending switch Si, Ef:

Y when the switchv reaches itsrncrmal position after the transmission of the first series of code impulses, wiper 113 will engage an ungrounded contact andthe circuit of relay 106 will be broken. On deenergizing, relay 106 again closes the shuntl around the impulsing Contact 123 at armature 120, and at armature 121 breaks the locking circuit of the stop relay 105. The latter relay, on deenergizing, again closes thecircuit o' the impulsing relay 107 at armature 119 and the transmission ofthe second series of code impulses is started. As indicated in the drawing, relays 105 and 106 are made slow-acting in order to introduce a brief time interval betweenthe-transmission of successive series oiimpulses, thus giving the selector switches time for their automatic trunk hunting operations. The second series of code impulses is nowtransmittedsimilar to the manner in which the first' series was transmitted. *When the circuit of the impulsing relay 107 is completedat armature 119 by the deenergization of the stop relay V105, the said impulsing relay begins to ture'120, prepares a locking circuit for the stop relay at armature 121, and closes the circuit of the sequence switch magnet 403 at armature 122. On the second energization of Y the impulsing relay 107 and on the succeeding energizations thereof, impulses will be transmittedover the switch control circuit comprising conductors 100 and 101 in the manner described in the foregoing, and by the time the stop wiper 114 arrives at the No 5 con tact in its bank av series kolf five impulses will have been transmitted. The No. 5 contact in the bank of the stop wiper 114'is now grounded and accordingly, the stop relay 105 is again energized, a locking circuit being established at armature v117 as before. Relay 105 also breaks vthe circuit of impulsing relay 107 at armature 119, closes the automatic rotary circuit at armature 116, and at armature 118 breaks the circuit of the sequence switch magnet 402. On deenergizing, the sequence switchl magnet advances the wipersk :to third position, whereupon ground is removed Jfrom the No. 5 contact in the bank of the-stop wiper 114 and is connected to the No. 4 contact. The

circuit extends from the grounded conductor 400-by way of wiper 404 in third posi tion, conductor 413, wiper 308 of the register switch J and tliecontact'engaged thereby, terminal 339, a `iuniper connecting this terminal with bus-bar No. 4,"and conductor 364 to the No. 4 contact in the bank ot the stop wiper.

" On the return of the sending switch S to normal after the transmission of the second series of code impulses, relays 106 and 105 are Y Y successively deenergized and the circuit of the impulsing relay 107 is again completed at armature 119. VIt will be unnecessary to go over the operation ot the sending switch again in detail in view of the preceding explanation, as it will be readily understood that the sending switch will now proceed to transmit a. series of itour impulses, relay 106 being energized on the iii-st step andstop relay 105 being energized as soon as the stop wiper 114 arrives at the No. 4 contact in its bank. The energization of the stop relay stops the transmission o'll impulses at the proper point, closes the `automatic rotary circuit for advancing the sending switch to normal position, and breaks the circuit of the sequence switch magnet 402, which was closed by the energization ot' relay 100. On deenergizing, magnet 402 advances t-he sequence switch wipers `from third to fourth position.

`Since there are only three series of impulses in the otlice code, the sequence switch S1 must now he advanced automatically through its fourth position in order to .prepare the circuits for the transmission ot' the thousands digit as soon as the sending switch S has restored to normal. This is accomplished automatically, due to the tact that terminal 338 is cross-connected to the bus-har X at the 1.1). F., instead ot to any ot the busbars which are associated with the bank ot `the sending switch. llVhen the sequences switch wiper 404 arrives in fourth position, a circuit is completed for the stepping` magnet 402 which extends from the grounded conductor 400 by way of wiper 404 in fourth position, conductor 414, wiper 309 of register switch J and the contact engaged thereby, terminal 338, a jumper connecting this terminal with bus-bar X, conductor 370, wiper 403 in fourth position, and through the interruptor contact and the winding of the stepping` magnet 402 to battery. Upon the closure of the foregoingl circuit, the stepping magnet 402 is energized momentarily and the( sequence switch Wipers are advanced to iifth or thousands position.

The three series of code impulses have now all been transmitted and the director is in readiness to start the transmission ot the impulses which correspondrto the registered digy its. In order that` the progress of the `call may be kept in mind, it may be statedthat in response to the second series of impulses, the wipers oi. the selector' E2, F ig. 8, are raised to the fifth level, whereupon a trunk line is selected which extends to a third selector which we will assume is the selector E3. -InV response to the third series Aoit code impulses, the wipers of the selector E are raised to the fourth level, and an idle trunk extending to the Torrington oilice is selected, the trunk taken for use being` assumed to be the one which extends by way of the repeater R to the selector E4. The repeater R is of a standard type and includes means such as a repeating coil by means of which the trunk is divided into two induct-ively connected sections. It includes also a line relay operated over the incoming section to repeat impulses into the outgoing section, and a slowacting release relay for grounding the extended release trunk conductor 57.

When the sequence switch S1 is automatically advanced to the iii-th or thousandsposipulses which oorrespondsto the thousands digit of the number is not started unless this digit has been registered, for unless the register switch M1 has completed its operation there will be no ground on conductor 421.

Under ordinary circumstances, however, the v calling subscriber will have completed the dialling of the thousands digit before the sending switch has completed the transmis sion of the series of code impulses, and assuming that this has been done in the present case, when the sending switch S arrives in normal position after the transmission of the iinal series of code impulses, the deenergization of the stop relay 105 will. be effective to again close the circuit of the impulsing relay 107. Sincethe thousands digit in the number is digit 2, the wiper 244 of the thousands register M1 is now standing on the second contact in its bank, and since the wiper 244 is now grounded by way of the wiper 404 oi the sequence switch S1, there will be a ground on the No. 2 contact in the bank of the stop wiper 114. It follows that in the next operation of the sending switch S, two interruptions will be produced in the control circuit, similar to the manner in which the several series of ycode interruptions were produced. These interruptions or impulses are received at the repeater R, F ig. 8, and are repeated over the interolice trunk line to the incoming selector EJe in the Torrington otce, which operates to raise its wipers opposite the second levehwhereupon an idle trunk is selected extending to a third selector which we wiil assume is the' selector During the operation of the sending switch in transmitting the thousands digit of the number, the stepping magnet 402 oi the qucnce switch S1 is energized and deenergized in the usual manner and advances the se quence switch wipers to the sixth or hundreds position. The movement of sequence switch wiper 404 disconnects ground from the wiper 244 of thethousands register M and connects ground to the wiper 245 of the hundredsregister M2 by way of conductor 416; ri'ssumingv that the calling subscriber has already dialled the hundreds'digit the conductor 422 will now have a ground oni it, causing the sending switch to restart immediately vwhen the stop relay falls back.. Since the' hundreds digit in the number is the digit 3, thereA will now be a ground on the No, 3 contact in the ner in order to advance the sequence switch wipers to the seventh or tens position. Assuming now that the calling' subscriber has completed the dialling ot the tens digit, conductor 423 will be grounded and wiper 246 will be standingon the No. 4 contact its bank, thus extending a ground to theNo. 4 contact in thebank of .the sending switch S;

' A series offour impulsesis accordingly transmitted by the sending switch, and is repeated lby the repeater R to the connector H in the Torrington oliice, which accordingly raises its wipers in the well-known manner lto the lliourth level ot bank contacts. The sequence switch magnet `402 is energized and deenergized in the usual manner during the trans mission of the impulses corresponding to the tens digit, and advances thesequence switch wipers to the eighth or units position with the result that wiper 404 places a ground on thewiper 247 ofthe units register Mt. lAssuming thatthe final digithas been dialled by Y the calling subscriber, conductor 424 will now be. grounded, the sending switch. AS will be started on its tinal operation and since wiper 247 is in engagementiwith the No` 5 contact inV bank, aseries of five impulses will be transmitted. kThe last series of impulses is repeated by the repeater R to' the connector H which is operated in the usual manner to' rotateits wipers into connection with the line extending to the station A1.

usual manner and the bell at thecalled station is operated to notify theV subscriber that he is wanted. ln the foregoing explanation it has been assumed each time that when the sending j switch arrives at `normal position after the istration of the rnext succeeding digit. e be understood, et' course, that in case there is transmission of a digit theV calling subscriber has already completed' th'e'ldialling and reglt will l Upon the completion of' vthe connection tothe called line, a signalling f circuit is established in the connector in the any delay on the part of the calling subscribi er, the sending switch will eventually catch up with him and that in such a case the restarting of the sending switch will be postponed until Yanother digit has been'registered.

The energization and deenergization of the sequence switch magnet 402 duringthe transmission ot' the final series of impulses causes the sequence switch wipers to be advanced to the ninth or switching position, whereupon. the following circuit is established for the switching relay 112: from groundby way ot sequence switch wiper 400 in switching position, conductor 420, contacts controlled by armature 189, and the winding ot relay 112 to battery. On energizing, relay 112 establishes a locking-circuit for itself Vat armature 139, breaking its initial energizing circuit at the same time, opens the circuit of relay 107 atarmature 140, removes the shunt from resistance 141 at armature 13'?, and at armature 138 disconnects conductor 103 from conductor 202 and connects the former conductor to ground` This latter operation coinpletes circuit for the switching relay 13 in the first selector trunk as follows: troni ground by'way of armature-138, conductor 103, bank contact 92, Fig. 1, wiper 88, workcontact of armature S3 and the said arma- .L l, conductor 62, contact springs controlled by armature 16, and the winding of the switch-A ing relay 13 to battery. Upon energizingpiii- 13 establishes a locking circuit tor itself at armature 10, connects the trunk conductors 10 and 12 with trunk conductors 20 and 22, respectively, at armatures 14 and 18, and

disconnects the said trunk conductors 10 and 12 from conductors 60 and 61 respectively, at armatures 15 and 1'?. A special adiustment of thevcontact springs or" relay 1S is essential in orderl to secure a qi'iiet'switcliing through operation. rlhe relay should be so adjusted that the springs represented Aby armature levers 14` 16,`and'18 'engage their nworking contacts first, as a'resultV of which ure, armature lf3 and its working contact ico c Aiiovrr the calling subscribers line will be connect ed to the windings of the line relay of the repeater in multiple with the switch control circuit in the director, and-in multiple with` line relay 64 ot the director selector l?. The resistance 141 is inserted in the control cir*- cuit bv the operation of the switching rela 112 inthe director in order to prevent short ciif'cuitins` or'frthe subscriberle line and the ob: jectionable noisey iii the receiver which would occur it short circuiting should take place.

An instantatter armatures 14 and 18 en their working contacts, ythe co el c extending to the director is cut and iin nally, just before `the relay is fully operated, armatures 15 and 17 disengage their resting contacts. The latter operation disconnects e line relay 04 and completes the .switching 'operation by which the calling,subscribers 

